Methinks you are close to the truth jags
Further road test:
I was cycling up to the lake District last weekend to meet up on a family get together, soon as I got out the door the heavans opened up, it was torrential.....
I managed to make it to Preston where I caught a train for the rest of the journey
As I boarded the train the headlight was flickering, I tried to turn it off but it wasnt having anything of it, finally I was able to turn it off by pulling out the usb charger cable.
The light worked fine after that, further tinkering revealed that the usb charging facility doesnt like rain, it was knackered.
I have brought it indoors now and dried it out, tomorrow I will check it out.
So in summary, charging in rain is not reccommended.
I am thinking of a plastic bag and some elastic bands for the next time it rains.
Some other observations from that horrendous trip:
1. Gloves were needed, my hands were slipping on the handlebars
2. The Carradry bags were waterproof
3. The saddle bag was damp inside
4. Rain on a bike helmet causes an itchy head which cant be scratched...
5. Trains are your friend
6. I now realise the importance of mudguards.
Ian